1. Bring milk, cream, and salt to a rolling boil while stirring. Reduce to a simmer and add lemon juice. Simmer for 2 minutes while constantly stirring. Strain through cheesecloth and let sit for 3 hours in the refrigerator. Use as you would any store-bought ricotta.
2. Place water in a medium bowl, sprinkle with yeast. Let stand until foamy, about 5 minutes. Stir in flour, oil, and 2 teaspoons coarse salt until dough forms. Turn out dough onto a lightly floured surface and knead until smooth. Transfer to a lightly oiled bowl, and cover with plastic wrap. Let the dough stand in a warmer until it doubles in volume. Preheat the oven to 350°F. Divide dough into 8 equal pieces, cover with plastic wrap. Roll out one piece to roughly 4 by 10 inches on a lightly floured surface, transfer to a parchment-lined baking sheet. Brush with extra virgin olive oil, sprinkle with sea salt and herbs. Repeat with remaining dough. Bake until lightly golden brown. Let cool.
3. Cut all vegetables into 1/2-inch pieces, keeping vegetables separate. Toss each vegetable separately with olive oil and roast at 400°F until golden brown. Let cool.
4. Top each flatbread with 1/8 cup of ricotta and 1/3 cup of roasted vegetables. Bake at 400°F for 5 minutes.